Mid to high pitched voice with a Trans-Atlantic accent. I put french for the accents because that or British works too.

(annoyed) "There is a reason why we have a bell over the door."

"Oh, you're all too kind. I was simply inspired by Twilight's amazing magical abilities. That's where all the sparkle and shine on her outfit came from! As for the star gemstones and diamonds, they were inspired by her cutie mark."

"It has been quite a long time since we've been to a formal Canterlot party like this. I'm sure it will be wonderful."